On-off indicator circuit



Sept. 9, 1941. wR|GHT 2,255,637

ON-OFF INDICATOR CIRCUIT Filed Sept. 50, 1939 l l l lgl'k fi darmer I i I i A ll' 'Il I. 0 $3 IBnventor \QQQQQ/ I m m I 4 I I (lttorneg Patented Sept. 9, 1941 ON-OFF INDICATOR CIRCUIT Antony Wright, Norristown, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application September 30, 1939, Serial No. 297,208 v 2 Claims.

The present invention relates to an on-ofi' indicator circuit for radio receiving apparatus and the like, and has for its primary object, to provide an improved on-oii indicator of the electrical type for battery operated radio and like apparatus, which is economical of current consumption to replace current consuming indicator devices such as pilot lamps ordinarily used.

It is also an object of the present invention, to provide an on-ofi indicator for battery operated receivers and the like, which provides an illuminated indication when energized and which consumes substantially no battery power.

It is also a further object of the present invention, to provide an improved on-off indicator for operated type, which consumes substantially no current and which is'of the intermittent flashing type being thereby further eflective in conserving battery power while providing a dynamic indication when energized.

In battery operated radio receivers and the like, the number of amplifier and other tubes employed is reduced to a minimum to conserve battery power, and for this reason such apparatus is rarely provided with a pilot lamp which remains on while the apparatus is energized.

Mechanical indicators do not attract the eye and pilot lamps and the like consume a large proportion of battery power. Therefore, without pilot lamp or indicator, it often happens that the apparatus is unintentionally left on and in an operating condition when it would otherwise be turned off, and thereby wasting battery power.

The invention will, however, be better understood from the following description when considered in connection with the accompanying drawing, and its scope is pointed out in the appended claims.

In the drawing, the figure is a schematic circuit diagram of a radio receiver provided with an on-ofl indicator circuit embodying the invention.

Referring to the drawing, the radio receiver circuit illustrated may be taken to represent any radio or other apparatus embodying amplifier tubes and adapted for battery operation and, by way of example, comprises a tuned signal input circuit I and a tuned oscillator circuit 8 each provided with a variable tuning capacitor "I having a common tuning control means I on the control panel 9 of the receiver and the usual tuning dial l and indicator Ii.

The oscillator and signal input circuits are through a suitable intermediate frequency output transformer ll.

Audio frequency signals from the diode are derived from the diode output resistor l8 which is ln'the form of a potentiometer or volume control device having a movable volume control conradio receivers and like apparatus, of the battery tact l9 coupled through a capacitor 20 with a control grid 2| in the tube iii. The grid is provided with a grid resistor 22. A. V. C. potentials are also derived from the resistor l8 through the lead indicated at 23. The tube I6 is provided with an output anode 24 coupled through suitable audio frequency coupling means 25 to an audio frequency output tube 26- which supplies the amplified signal output to a loudspeaker 21 through an output coupling transformer 28.

The tubes are all of the battery operated type having filament type cathodes 29, each connected to ground or a common return circuit for the receiver indicated at 30 and to a common filament supply lead 3|, whereby the filaments are connected in parallel between ground and the lead 2 I The filament circuit is energized from a suitable single cell battery 32 connected with the terminals 33 and 34, which are respectively connected to ground and to the lead 3|, the latter connection including an on-off switch 35 connected with and operable by the volume control device i8-l9 as indicated, whereby the switch 35 is opened as shown, when the volume control contact I9 is moved to a position for substantially minimum volume. The anode and screen grid circuits of the several tubes, indicated at 36, are also connected in parallel to a positive anode supply lead 31-38, the latter being connected through a switch 39 to the positive 13 supply terminal 40 of the receiver.

The negative B supply terminal is indicated at ll and is connected through a lead 42 and a bias potential supply resistor 43 to chassis or ground II. The B supply battery is indicated at 45 being connected between the terminals 40 and II.

The volume control device I9 and the switch 35 are also connected to operate conjointly with the switch 33 whereby the latter is opened and closed simultaneously with the switch 35, the control being provided by the usual volume control knob indicated at 46 on the front panel of the connected with an oscillator-detector or mixer receiver and the operating connection being indieated in the drawing by the dotted connection 41.

It is obvious that with a receiver or other electrical apparatus of this type having battery 1 power for both the filament and high voltage anode circuits, conservation of energy is important. Therefore, as hereinbefore considered, current or energy consuming devices as indicators 3 are not permissible for economical operation and ithe lack of any indicator may often result in g large continued operation of the apparatus after In accordance with the invention, an indicator I H8 is provided adjacent to ,or within the tuning idial area, whereby it may be observed through capacitor provides a relatively low cost indicator circuit for battery operated apparatus. In practice, the resistor 5| may be of the order of 4 megohms and the capacitor '52 may be or the order of .1 mid. with with a positive B voltage of 90 volts between the terminals 40 and H,

indicator circuit is negligible.

1 the dial, and comprises a neon tube having elec-.

p j trodes 49 connected with and controlled by relaitiv'ely highvoltage between the B supply lead 31 and the negative B supply lead 42 in the re- "ceiver,'together with a time delay or filter network comprising resistance and capacitance connected with the tube.

negative B supply lead 42 while the other electrode is connected through a series filter resistor 5| with the positive B, supply lead 31. A capacitor 52 is connected in parallel with the electrodes 49 of the tube 48.

39is turned on and the receiver is energized, the neon tube flashes intermittently as the volt-"' age across the capacitor 52 in successive cycles which is lower than the particular B battery or ianode potential employed in the apparatus, and discharges through the tube. The flash discharges the capacitor and the tube is normally darkened while the capacitor is recharging and 117116 cycle repeats causing a continued flashing j and a visible indication of the dynamic type that 3 With this arrangement, when the switch In the present example, one electrode 01' the ,i tube 48 is connected through a lead 50 with the circuit, a controlling capacitor connected in par- 1 builds up to the breakdown potential of the tube, ,1

hence the current or energy consumption or the I claim as my invention;

1. In an A and B battery operated radio receiver, an on-ofi' indicator circuit comprising a neon type tube having a flash-over voltage lower than the anode supply voltage of said receiver, an anode voltage supply circuit for said receiver comprising a positive and a negative, lead, a switch in one of said leads. for energizing said circuit, a controlling capacitor connected-in parallel with said tube between said positive and negative supply leads, and a serieshigh resistance control element in said connection whereby said tube flashes intermittently at a predetermined rate when said switch is closed to energize said circuit.

2. In an A and B battery operated radio receiver, an on-ofi indicator circuit comprising a neon type tube having a flash-over voltage lower than the anode supply voltage of' said receiver, an anode voltage supply circuit for said receiver 5 comprising a' positive and a negative lead,' a

switch in one; of said leads for energizing said 1 allel with said tube between said positive and negative supply leads, and a series high resistance control element in said connection whereby said tube flashes intermittently at -a predeter-.

' mined rate when said switch is closed to energize said circuit, said high resistance element having a resistance greater than 1 megohm whereby the substantially negligible.

energy cons ption or said indicator'circuit is ANTONY WRIGHT. 

